Bike keeps shifting gear on me...:(

Hi. When I am riding my Surly, and am at the higher gear...2-7 or 2-8 or 2-9, the chain doesn't seem to want to stay in gear.....It hops down, it hops back up....totally annoying and affects my rhythm......SO I stay down at 2.6 or go to 3.1............Ni sure of the terminology, so I hope someone understands what I am saying. Can someone explain what is going on and what I might need to do ? Thanks

 

Sounds like your rear derailer needs a bit of tuning.
If you are on the 9nth gear, and the chain is trying to go to 8th, turn the barrel adjuster counter-clockwise. You’ll find one either at the shifter or at the derailer: or both.

 

Barrel adjusting. Doubt the H-L limit needs adjusting but I would try the fine tuning utilizing the barrel adjuster first.

 

Sometimes that happens because the gear and chain is worn out and needs replacing. So if it jumps even though it is properly set up, that is the likely reason.

 

and sometimes the derailleur is bent. Most likely out of adjustment as previously stated.

 

If the bike is ghost shifting the cable is out of adjustment, this happens with brand new cables as they stretch till they get settled in, and it happens to old ones as they near the end of their life.

https://www.bing.com/videos/search?...294597DE8D2C1FF2161D294&view=detail&FORM=VIRE

It can also happen if the derailleur hanger is bent or the derailleur is out of alignment with the cassette.

 

Your problem may well be a misaligned rear derailleur. To find out, you would have to unscrew the derailleur from the hanger (you can leave the chain on and just leave it hanging). There is a special tool that allows you to measure the alignment. You need to check four points on the wheel. It will be the lowest, the highest and the front and back of the wheel, all at the same height on the rim. The tool also allows you to bend the derailleur hanger. Once it is straight you may have to reset your limit screws and cable tension. This will solve the problem almost all the time.

 

One thing that happened to me, actually impressed me not figuring it could happen.

My bike was going in and out of adjustment no matter how much I adjusted it. Turns out that if I looked inside the lever, I could see that the cable was starting to fray right at the bead. Surprised me as I would have never thought to look there.

So in other words, look there! Could be a cable beginning to fray.

Also the worn chain on cog set thing. And the barrel adjuster tension on the cable.

Easy rear der cable adjustment. Shift gears to outermost cog. Make sure it is corresponding to the shifter, last click, last gear. I've been fooled before.

Once certain it is in synch, turn the barrel adjuster so that it starts clunking and starts rubbing the wall of the next cog up (almost as if it is going to begin changing up a gear). Once you hear or see the rub, back the barrel off about 1/4 to 1/2 turn. That should put you right in the ball park. Maybe a hair this way or that way if needed.

I've done this for several cyclists on the road who were having trouble. Works well unless there is a problem. Then look at cables, etc.